The present invention relates to a hydraulic pressure control device of an automatic transmission and a hybrid drive device having the hydraulic pressure control device.
There exists a hydraulic control apparatus for an automatic transmission that is mounted in a vehicle such as an automobile or the like. In the hydraulic control apparatus, when a shift position and/or shift range is changed from a non-travel shift position and/or shift range (neutral position, parking position) to a travel shift position and/or shift range (drive position, reverse position) due to a shift lever operation by the driver, clutches and brakes are engaged by supplying engagement pressures to the hydraulic servos of the clutches and the brakes that are to be engaged. On the contrary, when changing from a travel shift position and/or shift range to a non-travel shift position and/or shift range, the disengagement of the clutches and brakes is carried out by discharging (draining) the engagement pressures of the hydraulic servos of the clutches and the brakes that are to be disengaged.
In such a hydraulic control apparatus, a valve is interposed on the oil paths that supply the engagement pressures for selectively guiding and regulating the original pressures, such as the line pressure and the range pressure. Normally, when these engagement pressures are discharged, the engagement pressures are drained via such valves by reversing the flow of the oil paths that supply the engagement pressures. However, problems occur, in particular, when the viscosity of the oil is high at low temperatures. The distance of the oil paths as described above becomes a resistance, the draining slows, the disengagement of the clutches and brakes is delayed, and there is a concern that travel torque will be transferred instantaneously (what is referred to as “residual engagement”) even though the shift position and/or shift range is in a non-travel shift position and/or shift range.
Such a phenomenon is particularly undesirable in the reverse travel direction. Enabling the engagement pressure of the hydraulic servos of the engaging elements that are engaged in the reverse travel shift position and/or shift range to drain quickly has thus been proposed (refer, for example, to Japanese Patent Application Publication No. JP-A-2001-343067). Here, in oil paths that supply engagement pressures to the hydraulic servos, a switching valve (refer to reference numeral 61 in FIG. 5) is provided on the hydraulic servo side, and the oil path up to the hydraulic servo is communicated with a drain port by switching the switching valve by using the signal pressure of a solenoid valve (refer to reference numeral S4 in FIG. 5). The draining is more rapid than the draining via the oil path that supplies the engagement pressure, and thus a quick draining becomes possible.